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CRTS Discovery of a very energetic Type IIn Supernova

ATEL # 2010; A..A. Mahabal, A.J. Drake, S.G. Djorgovski, M.J. Graham, R. Williams, W. Max-Moerbeck (Caltech); M. Catelan (PUC, Chile); E.C. Beshore, S.M. Larson, A. Gibbs, R. Kowalski, A. Boattini, R. Hill (LPL/UA); E. Christensen (Gemini Observatory); V. Mohan, A.N. Ramaprakash, A.K. Kembhavi (IUCAA);
on 10 Apr 2009; 22:45 UT
Distributed as an Instant Email Notice (Request for Observations)
Password Certification: Ashish Mahabal (

Subjects: Optical, Nova, Supernova, Transients

The Catalina Real-time Transient Survey (CRTS) has spectroscopically characterized CSS080928:160837+041626 (ATel 1768) as a Type IIn SN at z~0.041 using the SMARTS 1.5m telescope using Observations taken on March 27th UT with the following results:

IDRADec TypezDisc. ATel
CSS080928:160837+04162616:08:37.2304:16:26.7 IIn 0.041 ATEL#1768

The object was first marked as a transient by CRTS on 2008-09-28 (unfiltered mag=17.7). It was also present in the 2007-09-13 images, but blended with the brighter star nearby and hence not detected as a transient. Palomar-Quest images from 2007-02-24 do not reveal the presence of the SN. GALEX data from 2008-06-05 shows a well-detected source at this location (NUV 19.93+/-0.04, FUV 21.18+/-0.09). It was not seen in AIS images from 2004-05-17 indicating a brightening in NUV by at least 2.5 mags. Coadded images from SDSS (all filters) reveal the presence of a possible faint host at the location. Assuming that the galaxy has r=23, at z=0.041 it translates to M_r=~-13, almost a 100 times dimmer than the LMC.

Palomar 60-inch (P60) data form 2009-03-21 reveals that it is still bright (r=17.60+/-0.04). It has stayed bright for over 500 days, and rising much of the time. In fact the SMARTS spectrum with its Balmer lines (strong H-alpha, H-beta, H-gamma), He I lines (5876, 7065 and possibly others), and an absence of Oxygen lines reveals it to be much more like SN1994Y at T=30 days (Filipenko A.V., ARAA, 1997, 35, 309-355, Fig. 14). There is also some evidence of Fe-I emission and the H-beta shows a P-Cygni like profile. The maximum P60 r-band magnitude was ~17.2 suggesting an absolute magnitude ~-18.8. The evidence is consistent with a type IIn supernova possibly with high density circumstellar material.

Additional observations are requested.

All current candidate and confirmed SNe as well as finding charts can be found here.

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R. E. Rutledge , Editor
ATEL Mirror v1.0 Updates